In the field of digital logic, extensive use is made of well known and highly developed complementary metal-oxide semiconductor (CMOS) technology. As CMOS has begun to approach maturity as a technology, there is an interest in alternatives that may lead to higher performance in terms of speed, power dissipation computational density, interconnect bandwidth, and the like. An alternative to CMOS technology comprises superconductor based single flux quantum circuitry, utilizing superconducting Josephson junctions, with typical signal power of around 4 nanowatts (nW), at a typical data rate of 20 gigabits per second (Gb/s) or greater, and operating temperatures of around 4 kelvins.
A non-destructive readout (NDRO) circuit is a circuit that can retrieve a stored information state (e.g., one or multiple bits) for transmission to other circuitry for processing or output without erasing, destroying, changing, or otherwise corrupting the stored information state. For the purposes of this description, the term NDRO should not be interpreted to include circuits that destructively retrieve a stored information state but then thereafter perform a restorative write-back.
Reciprocal quantum logic (RQL) is a family of low-power superconducting circuits. In wave-pipelined RQL, a logical “1” can be encoded as a positive single flux quantum (SFQ) pulse followed by a reciprocal negative pulse, whereas a logical “0” can be encoded as the absence of either such pulse.